Motor-controlling mechanism.



No. 738,173. PATENTED SEPT. a, 1903.

. c. E. ENNES. MOTOR CONTROLLING MECHANISM.

APPLIOATION FILED SEPT. 22, 1902.

H0 MODEL. 2 SHEETS-SHEET 1- N0 MODEL.

' lZc'buwaew- PATENTED SEPT. 8, 1903. G. E. ENNTES.

MOTOR CONTROLLING MECHANISM.

APPLIUATION FILED SEPT. 22, 1902.

' 2 SHEETS-SHEET 2-.

GER/ES F'IELD m: nnnnn \s PETERS co. puorcpumo. wAsmNowN. nv c.

UNITED STATES Fatented September 8,

PATENT OFFICE.

CHARLES ENNES,"OF CHICAGO, ILLINOIS, ASSIGNOR TO OTIS ELEVATOR COMPANY, OF NEl/V YORK, N. Y., A CORPORATION OF NEW JERSEY.

MOTOR-CONTROLLING MECHANISM.

SPECIFICATION forming part of LettersPatent No. 738,173, dated September 8, 1908.

Application filed September 22, 1902. Serial No. 124,317. (No model.)

To all whom it may concern Be it known that I, CHARLES E. ENNES, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois,havein vented a new and usefulImprovement in ll/Iotor-Controlling Mechanism, of which the following is a specification.

This invention relates to motor-controlling mechanism.

The object of the invention is to providea motor-controlling mechanism which is simple in construction and efficient in operation.

A further object of the invention is to provide a controllingmechanism in which is combined a pressure medium and electrical devices for controlling the same.

A-further object of the invention is to provide a switch mechanism actuated by hydraulic or other pressure, which pressure is controllable electrically or otherwise in any suitable manner.

Other objects of the invention will appear more fully hereinafter.

Theinvention consists, substantially, in the construction, combination, location, and arrangement of parts, all as will be more fully hereinafter set forth, as shown in the accom panying drawings, and finally pointed out in the appended claims.

Referring to the accompanying drawings, and to the various views and reference-signs appearing thereon, Figure 1 is a view in elevation, partsin section, showingthe mechanical construction and arrangement embodying the principles of my invention. Fig. 2 is an enlarged detail-view in section on the line 2 2 of Fig. 1. Fig. 3 is a detail view of the switch for controlling the circuits of the electrical part of the apparatus employed in connection with my invention. Fig. 4 is a detail view in section on the line 44 of Fig. 3. Fig. 5 is a View in diagram, illustrating the electrical action of the apparatus and the circuits controlled thereby.

The same part is designated by the sam reference-sign wherever it occurs throughout the several views.

I will first describe the mechanical construction and arrangement illustrated in Figs.

1 to 4:, inclusive, and afterward point-out the tureswitphes,saidswitchescooperating with [0.7

circuit connections controlled thereby and as indicated in Fig. 5.

Referencesigns A and B designate suitable chambers, suitably com municating with each other and with cylinders C and D. The cylinders C and D are of identical construction and arrangement, and therefore only one need be described. In each cylinder is arranged a piston E, the stem of which is connected to the core F of a solenoid G, so that when the solenoid is energized to move the core F thereof the piston-plunger E is moved longitudinally into the cylinder.

H designates a plunger or piston fitted to move incylinder C and suitably connected to the piston-plunger E in'any convenient manneras, for instance, bymeans of a chain J.

K designates a spring interposed between the plunger H and the piston-plunger E, the tension of said spring tending to separate said plungers, the chain or other connection J preventing too far a separation of these parts.

A pipe L delivers from the end of the cylinders C D above the plunger II into chamber A and thence through a pipe or other connection M into chamber B. The chamber B communicates by a pipe or other connection N with a chamber 0, and in the pipe or other connection'N is arranged to operate a plunger P, arranged to control the delivery-mouths of pipes Q, R, and S or the communications of said pipes with chamber B or pipe or other connection N.

A B designate cylinders in which operate plungers CD, respectively. Each plunger is exposed on one face to the interior of chamber A and is connected, respectively, to switches E F, which switches I designate line-switches, the arrangement being such that when a pressure is imposed upon the face 0 of pistons C D, which are exposed to the interior of chamber A, said switches are operated to close circuits between contacts a b and a b, respectively. Similarly communicating with chamber B are cylinders G H, 93 in which operate plunger-s J K, suitably exposed on one face to the interior of chamber B and respectively connected to switches L M, which switches I will designate armacontacts a 11 a b (#1), and 0. arranged in pairs, as indicated.

Communicating with chamber 0 are cylinders N O, in which operate plungers P Q, respectively. Connected to plungers P Q are arms R S, on which are supported contacts T \V. Contact T operates over resistance-blocks A and the contact W operates over resistance-blocks B The inner face of each of the pistons P Q, is presented toward the interior of chamber 0.

Communicating with cylinder N and at a point adjacent to its upper end is a pipe C said pipe delivering into chamber 0 adjacent to the communication of cylinder 0 therewith. In this pipe connection C are arranged valves D E to which are connected operating-rods F G respectively, said rods being connected and projected by the movements of an arm ll J or other movable part connected to move with the cores F of the magnet G G so that when either of said magnets G G is energized the corresponding rods F G are moved and valves D E are opened.

Arranged within chamber 0 are inwardlyopening valves, (indicated generally by reference-signs K L suitable stops being provided to prevent the outward movement of said valves. The valve K operates to close chamber 0 to cylinder N, while the valve L operates to close chamber 0 to cylinder 0, and the point of connection of pipe C from cylinder N is at a point between cylinder 0 and valve L The stops for valves K L and indicated, respectively, at 12 13, cause any pressure within chamber 0 to tend to maintain the valves closed. The valve K however, as most clearly indicated in Fig. 2, is composed of a plate M having holes or openings (indicated in dotted lines at N therethrough and which cooperates with a disk or plate 0 having similar openings or holes P therethrough, so that by suitablyplacing the plates M O to secure more or less registry of the openings P and N any desired degree of suitable pressure may be permitted to enter cylinder N to operate the plunger P therein. Similarly chamber B is provided with inwardly-opening valves Q R which operate when pressure is admitted to said chamber B to close said valves to prevent such pressure from being admitted from said chamber B to cylinders G H except through pipes Q and B, respectively, and which pipes communicate with pipe N through openings controlled by plunger P, which plunger is exposed to any pressure admitted to chamber B. In pipe Q is arranged a valve S and in pipe R is arranged a valve T These valves are so constructed and arranged that when they are both moved in one direction only one of them opens the passage it controls, and when they are both moved in the other direction only the other one opens the passage it controls. The operating-arms of these valves are connected together by a link A which is adaptcd to be engaged by cam-blocks B C", r0

spectively, carried by rods F G, and the arrangement is such that when magnet G is en ergized a rod F is projected endwise. The cam-block B engaging link A causes valve S to open to admit the pressure of an operating medium from chamber 13 to cylinder G when the plunger P is shifted suiiiciently to uncover the opening of pipe Q with pipe N, and whenever magnet G is energized to project rod Gr cam-block C engages link A to open valve T thereby opening communication of pipe R to cylinder H whenever the plunger P opens the communication between cylinder N and pipe R. In the same manner a valve D opening in wardly,cuts off communication between cylinder B and chamber A except through pipe S, the communication of which with the source of pressure is controlled by plunger P, as above explained. All of the plungers C, D, J, and K when operated by the pressure-operating medium are moved in their respective cylinders against the action of suitable springs E which tend to return the same when the pressure is relieved. The valves K L Q R and D are all arranged to open inwardly, so that when the pressure imposed upon said valves is relieved said valves may readily open to permit the parts to return quickly to their initial positions.

Reference-sign A designates generally the operating-switch and comprises an arm B carrying a contact-piece C insulated therefrom, and also a contact-piece D whichis in electrical connection with arm B. Contactblock C is arranged to cooperate with contact-strips c (1 cl, so as to complete electrical circuits between strip 0 and strip d when moved in one direction and to complete circuit between strips 0 and d when moved in the other direction, and contact-block D cooperates with contacts d (1 when moved in one direction and with contacts d d when moved in the other direction. This contactblock D should be of sufficient length to bridge all the space between contacts d d or contacts cl d The pipes L and M and chambers A and B are adapted to contain or to receive any suitable pressure mediumsuch, for instance, as water, alcohol, glycerin, or the like-and similarly pipe N and chamber 0 are adapted to receive an operating or pressure medium. I

prefer to employ glycerin for this purpose because of its permanency and freeness from evaporation.

The mechanical operation is as follows: When solenoid G is energized, the core F thereof is drawn into the coil of said solenoid, thereby projecting piston plunger E and through the spring K moving plunger H in cylinder C, and consequently imposinga pressure upon the pressure medium contained in the pipes and chambers. This pressure being transmitted through chamber A to plunger C in cylinder A actuates the line-switch M to close the circuit between contacts a b.

At the same time pressure imposed upon the operating medium causes plunger P to be forced through pipe N, so as to uncover the opening of pipe Q with pipe N and also the opening of pipe S with pipe N and of pipe R with pipe N. The energization of magnet G causes a projection of rod F and by reason of the engagement of cam-block B with link A shifts valve S into position to open pipe Q, so that the pressure-operating medium is shifted to pass from pipe N through pipe Q and into chamber B at a point to expose piston J thereto, thereby causing the armatureswitch L to be actuated to close circuit between contacts a b and a b and at the same time to admit pressure through pipe S into cylinderB to actuate plunger D, thereby actuating switch F, which I have designated the brake-switch, to close circuit between contacts Ct 12. The projection of plunger P through pipe N also forces the operating medium through the graduated or adjustable apertures of valve K into cylinder N and causes plunger P to gradually or slowly move through cylinder N, thereby raising arm R and causing contact T to travel over the resistance contacts or blocks A The movements of rod F under the conditions above described, while effecting an operation of valve D does not supply the pressure medium from cylinder N through pipe 0 to cylinder 0 when plunger P has been moved a sufficient height or distance to uncover the communication of pipe C with cylinder N, because the valve E which also controls pipe C has not been opened under the conditions above set forth. Consequently the above operation places the apparatus in whatlshallterm the position of slowspeed, the various parts and switches operated as described serving to complete the desired circuit connections for a slow speed, as will presently be more fully explained in connection with the operation of the apparatus. The above operation, it will be observed, leaves the armature-switch M in its initial or original position. Consequently the motor will operate in one direction, as the armatureswitch L controls the motor-circuits for operation in one direction and the switch M controls the motor-circuits for the motor to operate in the opposite direction, as will be more fully explained. In order to attainza high speed, the magnet or solenoid G is en ergized, thereby operating the core F thereof and projecting rod G and opening valve E and consequentlyadmittiug pressure through pipe C to cylinder 0 and operating plunger Q, thereby causing contact WV to cut out the remaining resistance controlled by resistance blocks or contacts B 1f solenoid Ghas been previously energized, as above explained, this action ofsolenoid G' willnoteffectan operation of valve T Consequently the motor will continue to run in the direction as controlled by armature-switch L. If, however, magnet G is energized first, then valve T will be opened.-

and armature-switch M will be actuated to control the motor-circuits to cause the same to revolve in the opposite direction, and a subsequent energization of magnet G will not effect this direction, and in any event, whether magnet G or G is energized first, the slow-speed resistance controlled by piston P will first be cut out, and the high-speed resistance controlled by contact-blocks B will not be cut out until both magnets G G are energized. When the magnets G G are deenergized, the cores F return by gravity or otherwise to the initial positions thereof, as indicated in Fig. 1, thereby causing the piston-plungers E to draw or carry with them the plungers H, thereby relieving the pressure on the operating medium and creating some degree of vacuum or suction, and the inwardly-opening valves D Q R K and L permit the operating medium to quickly exhaust or be restored to original condition, the parts to be restored to their initial positions. When the solenoid-cores F are drawn into the solenoid-coils, circuit is closed between contacts ff and f f by arms I'I J or otherwise and for a purpose presently to'be described.

Having now explained the mechanical construction and operation, I will now describe the electrical connections and operation, reference being had to Fig. 5. lVith the parts in the position shown in Figs. 1 and 5, suppose the operating switch-arm B is moved to the right for contacts or strips D d to be brought into electrical connection with each other. Thereupon the following circuit is completed: from main supply-wire A to contact a, wire 20, contact 0, through contactblock C to contact 61, through wire 21, the coils of magnet G, wire 22, contact d contact D ,armB ,wire 23 to the return-wire B thereby energizing magnet G and causing pistonplunger E to be operated and a pressure to be imposed upon the pressure medium, thereby actuating liue-switch-operating plunger C and causing said switch to close or bridge contacts a b. At the same time the armatureswitch L is actuated through the mechanical operation above described, thereby closing circuit between contacts A and B and also between contacts A and B Thereupon the following circuits are completed: from main supply-wire A to contact a, through the lineswitch E to contactb, wire 24, the shunt fieldwire 25 to main return-wire B also, the following circuit: from main supply-wire A contact a, wire 26, all of resistances A wire 27, all of resistance B wire 28,'the series field-wire 29, contact 19 contact a wire 30,

contact (t wire 3l,through the motor-wire 32, contact a wire 33, contact b contact a wire 34 to the return, thereby starting up the motor with the shunt field,the series field, and all the resistances in circuit. The actuation of brake-switch F, which takes place at the same time as the closing of armature-switch L, as above explained, causes the circuit to ergized to release the brake.

be bridged from contact a to contact I). Thereupon the brake-magnet circuit is completed as follows: from main supply-wire A contact a, contact 19, contact a, switch F, contact I), brake-magnet, wire 35 to return B The admission of the pressure to-cylin der N under the conditions noted actuates piston P and gradually cuts out the resistances A which I have designated the slow-speed, resistance in Fig. 5, and the motor continues to operate at slow speed with shunt and series field and armature in operating circuit and with the brake-magnet en- In order to attain high speed, the operating switch-lever B is moved to the right sufficiently far to enable the contact D to bridge the space between contacts 01 and 1 Thereupon the circuit condition above described remains the same; but in addition the current passing through contact d divides,part passing therefrom through contact-block D ,.switch-arm B and Wire 23 to return, and the other passing from block D to contact dflwire 36, magnet G wire 37, contactf,and thence across the space to contact f, when the core of solenoid G has been sufliciently energized to permit arm H to bridge the space between contact f and contact f, and thence through Wire 38, wire 23, and to return. Thereupon without derangement of any of the apparatus, as above explained, magnet G is energized, thereby causing rod G to be moved-endwise and opening valve E in pipe 0 and since valve D in the same pipe has previously been opened by the energization of magnet G it will be seen that pressure from cylinder N is admitted through pipe C to cylinder 0, thereby actuating plunger D therein and effecting a cutting out of the resistances B which I have marked the high-speed resistance, and the motor operates at high speed. If magnet G had been energized first, the only difference in the operation from that above described would be that armatureswitch M would have been actuated instead of armature-switch L, and this would have merely reversed the direction of current through the motor. Upon return of the operating-switch B to central position the circuits of solenoids G G are broken. The cores of said solenoids are thereupon permitted to return to initial position, effecting a reorganization of all the parts.

It is believed that the construction and operation of the apparatus shown and described and embodying the principles of my inven tion will be fully understood from the foregoing description.

It is obvious that many variations and changes in the details of construction and arrangement would readily occur to persons skilled in the art and still fall within the spirit and scope of my invention. I do not desire, therefore, to be limited or restricted to the exact details shown and described; but, Having now set forth the object and nature of my invention and a construction embodying the principles thereof, What I claim as new and useful and of my own invention, and desire to secure by Letters Patent, is-

1. In a motor controlling mechanism, a switch, pressure mechanism for operating the same, and electrical devices for controlling the pressure of the operating medium, said electrical devices also operating to control the supply of said medium to said mechanism, as and for the purpose set forth.

2. In a motorcontrolling mechanism, a pressure-operating switch-actuating mechanism, and electrically-operated means for controlling the pressure of the operating medium and its supply to said mechanism, as and for the purpose set forth.

3. In a motor-controlling mechanism, a

switch-actuating pressure mechanism including a cylinder, a piston operating therein, and electrical devices for controlling the pressure of the operating medium, said devices operating to control the supply of said medium to the cylinder to move said piston in one direction, as and for the purpose set forth.

4.. In a motor-controller, switch-actuating pressure mechanism normally inactive with respect to the switch, and electrical devices for controlling the pressure of the operating medium and its supply to said pressure mechanism, as and for the purpose set forth.

5. In a motor-controller, switch-actuating pressure mechanism, electrical means for controlling the pressure of the operating medium and its supply to said mechanism to operate the switch in one direction, and devices for restoring the switch to normal position, as and for the purpose set forth.

6. In a motorcontroller, switch-actuating pressure mechanism including a cylinder, a piston operating in said cylinder, pressurepipes containing a fixed quantity of operating medium and communicating with said cylinder, means for normally maintaining said piston in one limit of its movement, and electrical devices for moving said piston to vary the pressure of said operating mediu m, as and for the purpose set forth.

7. In a motor-controller, switch-actuating pressure mechanism including a system of pipes adapted to contain a fixed body of operating medium, a cylinder opening to said pipes, a piston operating in said cylinder, and electrical devices for operating said piston to effect a movement of said body of operating medium, as and for the purpose set forth.

8. In a motor-controlling mechanism, a series of switches, plungers or pistons connected to said switches for operating the same, a pressure mechanism for actuating said plungers,and including pipes or chambers adapted to contain a fixed body of operating medium, said pipes delivering to said piston, and means for moving said piston to shift the pressure medium in said pipes, as and for the purpose set forth.

9. In a motor-controlling mechanism, a

IIO

switch, a plunger connected thereto for operating the same, a pressure mechanism for actuating said plunger, and including pipes or chambers adapted to contain a fixed body of operating medium, said pipes delivering to said piston and electrical devices for moving said piston to control the pressure of said operating medium, as and for the purpose set forth.

10. In a motor-controlling mechanism, a switch, meansnormally operatingtoopen said switch, a pressure mechanism for closing said switch, including a system of pipes and chambers adapted to contain a fixed body of operating medium and means for controlling the pressure of said medium, as and for the pur pose set forth.

11. In a motor-controlling mechanism, a switch, means normally tending to maintain said switch open,pressure mechanism for closing said switch, including a system of pipes and chambers adapted to. contain a fixed body of operating medium and electrical devices for controlling the pressure of the medium in said pipes and chambers, as and for the purpose set forth.

12. In a motor-controlling mechanism, a switch, a plunger connected to said switch for operating the same, a cylinder in which said plunger operates, a pressure mechanism for operating said plunger in one direction including a system of pipes and chambers adapted to contain a fixed body of operating medium, means for normally opposing the pressure of said medium, and electrical devices for imposing a pressure upon said medium, as and for the purpose set forth.

13. In a motor-controlling mechanism, a series of switches, pressure'mechanism for actuating said switches including-a system of pipes and chambers adapted to contain a fixed body of operating medium, and means for controlling said pressure mechanism to actuate said switches in successive order, as and for the purpose set forth.

14. In a motor-controlling mechanism, a series of switches, means normally operating to maintain said switches in open position, pressure mechanism for operating said switches including a system of pipes and chambers adapted to contain a fixed body of operating medium, and devices for controlling the pressure-operating medium in said pipes to suecessively operate said switches, as and for the purpose set forth.

15. In a motor-controlling mechanism, a line-switch and an armature-switch, pressure mechanism for actuating said switches, and

means for controlling said pressure mechanism to operate said line-switch in advance of the operation of said armatu re-switch, as and for the purpose set forth.

16. In a motor-controlling mechanism, a line-switch and an armature-switch, pressure mechanism for actuating said switches, electrical devices for controlling said pressure mechanism to actuate said line-switch, and

line-switch and a brake-switch,pressure meehanism for actuating said switches, and elec- 'trical devices for controlling said pressure mechanism to actuate said line-switch in advance of the actuation of said brake-switch, as and for the purpose set forth.

18. In a motor-controlling mechanism, a line-switch, a brake-switch and an armatureswitch, pressure mechanism for operating all of said switches, and electrical devices for controlling said pressure mechanism to actuate said line-switch in advance of the actuation of said brake and armatureswitches, as and for the purpose set forth.

19. In a motor-controlling mechanism, a line-switch and armature-switches, said armature-switches arranged, when actuated, to control the direction of current through the armature, pressure mechanism for actuating said switches, and electrical devices for controlling said pressure mechanism to actuate either of saidarmature-switches at will and said line-switch in advance of the actuation of said armature-switches, as and for the purpose set forth.

20. In a motor-controlling mechanism, a line-switch, armature-switches for controlling the direction of current through the armature, a resistance-controlling device, pressure mechanism for actuating said switches and devices, and electrical devices for controlling said pressure mechanism, as and for the purpose set forth.

21. In a motor controlling mechanism, switches arranged to control the motor-circuits, resistance-controlling devices arranged in the motor-circuits,plungers for respectively operating said switches and resistance-controlling devices, pressure mechanism for actuating said several plungers, and electrical devices for controlling said pressure mechanism, as and for the purpose set forth.

22. In a motor-controlling mechanism, a plurality of switches, a pressure mechanism for actuating said switches, electrical devices for controlling said pressure mechanism, and inwardly-opening valves whereby said pressure mechanism is enabled to quickly restore the parts to normal position, as and for the purpose set forth.

23. In a motor-controlling mechanism, a system of pipes arranged to receive a pressure medium, means for imposing pressure upon said medium, and inwardly-opening valves arranged in said pipes and operating to permit the restoration of the parts to normal position upon withdrawal of the pressure imposed upon said medium, as and for the purpose set forth.

24. In a motor-controlling mechanism, a series of switches, a pressure mechanism including a series of pipes, plungers communieating with said pipes, said pipes adapted to receive a pressure medium, means for imposing a pressure upon said medium to operate said plungers, and inwardly-opening valves whereby when said pressure is removed the parts are'quickly. restored to normal position, as and for the purpose set forth.

25. In a motor-controlling mechanism, a series of switches, plungers for operating the same, pipes to which said plungers are eX- posed, said pipes adapted to receive a pressure-operating medium, means for imposing a pressure upon said 'medium, valves arranged in said pipes, by-passes around said valves, and means for controlling said bypasses, as and for the purpose set forth.

26. In a motor-controlling mechanism, resistances arranged in the motor-circuit and in sets, a plunger for Controlling each set, pressure mechanism for actuating said plungers, and means for controlling said pressure mechanism to actuate the plunger of one set of resistance devices inadvance of the other, as and for the purpose set forth.

27. In a motor-controlling mechanism, resistances arranged in sets, a plunger for controlling each set of resistances, a cylinder in which each plunger operates, a pipe comm unicating from one of said cylinders to the other, valves arranged? in said pipe connection, a pressure mechanism for actuating said plungers including a pressure-mediui'ncontaining chamber, means for creating a pressure in said chamber, said chamber communicating with one of said cylinders, and means for controllingsaid valves, whereby both of said plungers may be actuated successively, as and for the purpose set forth.

28. In a motor-controlling mechanism, a rheostat arranged in the motor-circuit, a plunger for actuating said rheostat, a cylinder in which said plungeroperates,achamberadapted to contain a pressure medium, a valve arranged to control the cpmmunication of said chamber and cylinder, means for imposinga pressure upon the operating medium contained in said chamber, and means for adjusting said valve to vary the speed at which said pressure mediumlis admitted to said cylinder, as and for the purpose set forth.

.29. In a motor-controlling mechanism, a plurality of switches arranged to control the motor-circuits, a pressure mechanism for actuating said switches and including a chamber, a pair of cylinders communicating with said chamber, a piston operating in each cylinder, electrical devices for operating either of said pistons at will, whereby when either of said pistons is operated a pressure is imposed upon the pressure medium contained in said chamber, valves controlled by said.

electrical devices for admitting said pressure medium to one or another of said switches according to which electrical device is in operation, all combinedand arranged as and for the purpose set forth.

30. In a motor-controlling mechanism, a line-switch, an armature-switch and a rheostat, a pressure mechanism for actuating said switches and rheostat'and including a chamber adapted to contain a pressure medium, valves for controlling the supply of operating medium to said armature-switch and rheostat, means for imposing a pressure upon the operating medium in said chamber, and means actuated coincidently therewith for operating said valve, as and for the purpose set forth.

31. In a motor-controlling mechanism, a line-switch, armature-switches and a rheostat, a pressure mechanism for actuating said switches and rheostat including a chamber adapted to receive a pressure medium, valves for controlling the supply of said medium to actuate said armature-switch and rheostat, a rod for operating said valves, electrical devices for imposing a pressure upon the medium contained in said chamber, said electrical devices'operating, when operated, to actuate said red, as and for the purpose set forth.

32. In a motor-controlling mechanism, a line-switch, armature switches for controlling the direction of currentthrough the armature, a brake-switch and a rheostat, pressure mechanism for operatingsaidseveralswitches and rheostat and including a chamber adapted to receive a pressure medium, valves for controlling the supply of said medium to said armature-switches and rheostat, a pair of solenoids each adapted, when energized, to impose a pressure upon said medium, and means actuated by said solenoids for operating said valves, all combined and arranged as and for the purpose set forth.

In witness whereof I have hereunto. set my hand, this l8th day of September, 1902, in the presence of the subscribing witnesses.

CHARLES E. ENNES.

\Vitnesses:

E. A. RUSSELL, H. F. FULTON. 

